Many vehicular lamps, such as vehicular headlights and fog lamps, have an irradiation unit which includes, for example, a light source such as an LED or a bulb, and a reflector. The irradiation unit is arranged inside a lamp chamber formed by a lamp body and a cover, and an aiming adjustment mechanism is provided for adjusting the optical axis of the irradiation unit with respect to the vehicle body. See, for example, Japanese Patent Laid-Open No. 2004-311224. The aiming adjustment mechanism is typically configured such that the front ends of a plurality of aiming adjustment screws protruded from the lamp body are fitted or screw-coupled to a support seat provided on the irradiation unit. Furthermore, the aiming adjustment mechanism is also configured to support the irradiation unit in most of cases.